In general, fuel cells are power generation type cells which generate electricity by combining hydrogen with oxygen. Fuel cells may continuously produce electricity as long as hydrogen and oxygen are supplied, differently from general chemical cells, such as batteries or storage batteries, and have no thermal loss, thus having 2 times the efficiency of internal combustion engines. Further, fuel cells convert chemical energy, generated by combination of hydrogen and oxygen, directly into electric energy, thus emitting a small amount of pollutants. Therefore, fuel cells are eco-friendly and may reduce worry about exhaustion of resources due to increase in energy consumption. Such fuel cells may be classified into a polymer electrolyte membrane fuel cell (PEMFC), a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), a solid oxide fuel cell (SOFC), an alkaline fuel cell (AFC) and the like according to kinds of electrolytes to be used. These respective fuel cells are basically operated by the same principle but are different in terms of kinds of used fuels, operating temperatures, catalysts, electrolytes and the like. Thereamong, since a PEMFC is operated at a low temperature, as compared to other fuel cells, and has a high power density and may thus be minimized, it is known that the PEMFC is the most useful in transportation systems as well as small mount-type power generation equipment.
One of the most important factors to improve performance of the PEMFC is to maintain a water content by supplying moisture of a designated amount or more to a polymer electrolyte membrane or proton exchange membrane (PEM) of a membrane electrode assembly (MEA). The reason for this is that, if the polymer electrolyte membrane is dry, power generation efficiency is rapidly lowered. In order to humidify the polymer electrolyte membrane, there are 1) a bubbler humidification method in which a pressure resistant container is filled with water and moisture is supplied by causing a target gas to pass through a diffuser, 2) a direct injection method in which an amount of moisture required for reaction of a fuel cell is calculated and moisture is supplied directly to a gas flow pipe through a solenoid valve based on the calculated amount of moisture, 3) a humidifying membrane method in which moisture is supplied to a fluidized bed of gas using a polymer separation membrane, and the like. Among these methods, the humidifying membrane method, in which a polymer electrolyte membrane is humidified by providing vapor to gas supplied to the polymer electrolyte membrane using a membrane selectively transmitting only vapor included in exhaust gas, may reduce the weight and size of a humidifier, thus being advantageous.
As a selectively preamble membrane used in the humidifying membrane method, a hollow fiber membrane having a large transmission area per unit volume may be used or a flat sheet membrane being advantageous in terms of acquisition of a uniform fluid flow may be used. A moisture supply apparatus to which a hollow fiber membrane is applied may be desirably used in a fuel cell system having a high capacity of 100 kW or more, which requires high integration, and any type of membrane may be used in a general fuel cell system having a capacity of 50 kw or less.
Technical development up to now has been concentrated upon improvement in efficiency of a selectively preamble membrane so as to achieve high integration of a humidifying membrane-type moisture supply module, but the present invention adds a physical device to a moisture supply module so as to maximize moisture transmission efficiency and to achieve high integration and manufacturing cost reduction effects therethrough.